A known worm wheel is disclosed in JP2002-310267A (hereinafter, refers to as a reference. The worm wheel is formed with resin and driven by a worm. The worm wheel is provided with: an engaging portion having a plurality of teeth engaged with the worm; and tooth spaces defined between the neighboring teeth and of which bottom surface is recessed radially inwardly. The worm wheel is structured by integrating two members divided perpendicularly to the axis thereof.
Generally at a resin molding with a die, undercut is formed by tooth spaces when the bottom surfaces of each tooth space is recessed radially inwardly. If the amount of the undercut is large, it may be difficult to die-cut the worm wheel after molding the worm wheel in the die, which structures the worm wheel disclosed in this reference with two members.
The worm wheel disclosed in the reference needs to be structured by resin-molding two members separately and by bonding the two members perpendicularly along the axis direction, thus leading to an inevitable increase of man-hours to connect two members.
As a worm wheel, which is not established with plural divided members, a resin base material of the worm wheel can be formed with toothed portions at a peripheral portion by cutting. However, the cutting work is not cost efficient and a certain improvement is considered to be necessary for this method from the viewpoint of productivity.
The present invention has been made in view of the above circumstances and provides a resin worm wheel manufactured with improved productivity.